False Speed-Limit Enacted in 1875

[Computer Guru]

OK, this is going to get marked as a non-bug since it's non-reproducible, but as a developer I know what it is

I was d/u at 52/10 - my max. I opened up the options dialog to check something, then *poof*.

As you can see from the picture, I went from top-speed downloading to upload-limit.

I have auto-upload speedcap on.

I don't have an explanation for this. I didn't touch any settings, it's a healthy torrent, I didn't change any values, I pressed "cancel" instead of "OK" or "Apply" and I don't know what happened.

I had to turn uTorrent off and back on because it's been some time now and still downloading below my upload - but I don't know if that is going to fix it.

(BTW, how the hell do you type uTorrent in linux? It feels so wrong constantly misspelling it, but alt+numpad doesn't work)

[Ultima]

IMHO, that it's not reproducible only gives us enough proof to say that it's a coincidence... The screenshot doesn't reveal anything, and it still doesn't seem to me like the download rate is getting limited by the upload rate -- otherwise, it would be hugging the limit like the upload rate is. To me, the weirdest thing in that screenshot is the fact that the download rate's line is broken in the middle

In any case, even though I doubt it's a bug, the people with the real final say are the devs, so I'll shut up about that

As for typing the µ... I never found an easy way to do so in Linux. I tried messing with the keyboard region settings, but it never worked out too well. I ended up having to copy and paste from the forum description up above.

[Switeck]

At one point, your graph suggests you turned off upload limiting entirely. Upload speed spiked at that point and fell a bit, then spiked and fell again. Then you set the upload speed to 10 KiloBYTES/sec. (Previously it seemed a little lower, about 8?) But for whatever the reason, even that "10" speed seemed a little too much to sustain for long stretches.

Shortly after upload speed was set to 10 KiloBYTES/sec and not long after it briefly reached that speed, your download speed fell like a brick. Your upload speed ALSO took a dip roughly the same time as the massive download dive. So my guess is your download became horribly slowed due to an upload overload...the peers/seeds uploading to you were no longer receiving SYN-ACK packets from you in a timely manner because your upload side was overloaded.

Perhaps you just are allowing too many connections (or half open connections) at once to push so close to your upload limit? You had 69 connections shown (seeds+peers) for the 1 torrent.

Have you tried checking how many failed partial connections your computer's maintaining when things go bad like this? (...using a tool like TCP View.)

[Computer Guru]

That was automatic upload speed re-negotiating for some odd reason.

[Ultima]

It's not odd. Auto-uplink throttling unthrottles every bt.auto_ul_interval seconds so that it can remeasure the network conditions.

[Computer Guru]

Yeah, but the odd thing is that auto-uplink killed my download until I restarted uTorrent. I left it open > 10 min. without it going back up. Within 3 min. of restarting it I had full speed again.

[Ultima]

I still say it was a coincidence. The fast peer(s) you were downloading from probably choked you. People also swear that µTorrent runs faster while activated and not minimized to tray, but the fact of the matter is, it doesn't run faster one way or another (unless your computer barely meets the minimum requirements for running µTorrent).

[Computer Guru]

I know it doesn't - I never have it activated myself.

I see what you mean - and you're probably right. Just wanted to throw this out there in case someone else had the same thing.

However, I highly doubt I was "choked off" because I'd been downloading for an hour+ without an issue, then all of a sudden it happened. I was on Linux, half_open set to 500, max connections to 90/120. Yes, they're high, but I've been using these very settings for months with brilliant results.

W/E.

I'm a developer myself, I know how it goes. It's difficult to do anything if it looks like a coincidence and/or cannot be reproduced. Thanks for the help anyway

[Ultima]

I tried (vigorously) to reproduce it, but couldn't. I just ended up opening and closing the Preferences dialog a bunch of times, to no avail

Anyhow, let's just hope it doesn't happen again (that it was just a coincidence)

[Switeck]

Please, for the sake of everyone ever possibly on torrents you connect to...

Please reduce your half open max to under 50.

As-is, your computer's devoting a considerable amount of upload bandwidth to hammering through 500 ips at once...possibly more, considering once a full connection is made but before file transfers begin the BitTorrent handshake has to be given!

Could this be how others see you on a torrent swarm?: (besides the fact it's a BitComet client)

http://forum.utorrent.com/viewtopic.php?id=23278

That alone would depress the usable upload bandwidth for uploading files/torrents considerably.

[Computer Guru]

I don't think so.

That's just the max half-open, right?

Seeing as my max-per-torrent is 80, and I already have a few, then it wouldn't be all those at once, no?

More so, how does this hurt the swarm? It's different from the bittorrent scenario, since I'm a legit peer doing both upload and download with a client that doesn't abuse connections. I'm just initiating more connections/second, and unless the peers I'm connecting to are looking for incoming connections (i.e. have room in the connection queue), then it's not hurting. And those that _do_ have connections to spare, it will benefit them too... Unless of course I'm missing something.

[Switeck]

The half open rate is continued TILL max connections per torrent (or global) is reached. This can mean you may likely be attempting more connections at once than you allow in total.

Because it's set so high, you can cycle through the entire ip list for every torrent and retry them again "quickly". TOO quickly in fact for most torrents, as seeds/peers on the torrent probably see your ip trying to connect to them again every couple seconds instead of the "proper" wait times set up by BitTorrent guidelines.

For people with marginal connections, if there's lots of ips "hammering on their door"...it can degrade THEIR performance even if no one else is affected. Certain software firewalls can even blue-screen Windows if the connection rate gets too high. Even if they reach connection max, it's no use. I've had max connections before and still the same ips repeatedly try to connect faster than once per minute.

[Computer Guru]

'kk

Didn't know that - I'll change it now

[Switeck]

Here's something crazy...I've set my half open rate to ZERO and µTorrent still works.

I don't start any connections, I just hop on a torrent and start waiting for others to connect to me. Because I'm not firewalled (as far as µTorrent is concerned only!), that often happens very rapidly...and I may still get 50+ connections in as little as 5 minutes.

A firewalled connection would want a reasonable half open connection rate, because others CAN'T connect to it. (Their "telephone" never rings.) But even in their case, there's little need to be able to replace every possible connection they allow (connection max) in under 30 seconds. Even a half open rate of 5 could do between 10-150 connections in 30 seconds. It varies so much because if the other end refuses to respond, it may take the full timeout period.

[Computer Guru]

Interesting.

But definitely _having_ a half-open limit (greater than zero that is ) DOES help - whether or not you are firewalled.

You must have a fast connection, I have 512/128, and can never get full connections in 30 seconds. With 8 half-open, it takes 5 minutes or so, with 50 around a minute.

[AllGamer]

I agree it is pure coincidence thing, *sort of*

As i understand Torrents are like "playing the music chair game" every little stupid thing can make you lose the seat (fast seeds / peers), and you are left standing until another seat becomes available.

it is just like back in the good old times using 28.8 kbps modem to download something, and some how you get interrupted, and by the time you reconnect back to the BBS somebody else took your spot.

[Switeck]

You set your half open rather high, and it'll have to stay high to make up for the connections it's causing you to lose.

I normally have my half open rate set to 4 or 8, though on rare occasion I've set it as high as 20 for a couple minutes on torrents with 1000's of seeds+peers. I didn't need to leave it there because once I got 50+ connections I tend to lose them pretty slowly...about 5 per minute, which even a half open rate of 4 can hold onto EASY and then some.

I only set half open to 0 as a test. But the default setting of 8 is more than enough for even 10 megabits/sec symmetric lines...assuming you don't have connectivity issues!

If you're firewalled, you'll NEED a much higher half open rate just to maintain 50 connections on average. Like 20 half open...

Also, certain torrents tend to attract fewer 'stable' ips. Dunno why it is, but anyone in Canada, Australia, England, and much of Europe have terrible stability issues.

[AllGamer]

Also, certain torrents tend to attract fewer 'stable' ips. Dunno why it is, but anyone in Canada, Australia, England, and much of Europe have terrible stability issues.

I've a pretty good idea, and it seems like to be all ISP related, all those places practise network traffic shaping.